Figure 5. Cryo-SEM images as a function of WOin the microemulsion with lignin at fixed RP/W value of 4.78 with different WO value (wt. %) of (A) 9.2, (B) 13.3, (C) 20.9, and (D) without lignin in (A).
Hence, it suggests that lignin macromolecules are able to facilitate the formation of bigger and discrete microemulsion droplets, and then to have this SFME system stabilized due to the aggregation of amphipathic lignin at the surface of the microemulsion droplets, which can improve the contact between lignin and hydrosoluble catalyst for the following lignin oxidation. Additionally, by comparison the microemulsion droplets with and without lignin, the size distribution of the former is less concentrated than that of the later (Figure S3C), which can be attributed to the high dispersion degree of lignin macromolecule (Table S1), resulting a wider size distribution of droplets in the microemulsion with lignin.